1. Field of the Invention
The present invention relates generally to regenerative type furnaces, and more particularly to improvements in regenerative heat exchange structures and the bricks or blocks employed in constructing such structures.
2. Description of the Prior Art
Such heat exchange structures are used with various types of furnaces including those for steel and glass making. The present invention has particular utility in glass melting furnaces and will be described herein in connection with the checkers of such furnaces. However, it will be readily apparent that it may as well be employed with various other types of furnaces.
As is well known, present day flat glass is conventionally produced in a continuous tank-type melting furnace, wherein raw batch materials and scrap glass, or cullet, are continuously delivered to the charging end of the furnace, melted and refined as they move through the furnace, and then withdrawn from its delivery or working end as a continuous ribbon. In furnaces of this type, heat for melting the raw batch material is provided by flames directed through a series of ports arranged along each opposed longitudinal side of the furnace above the mass of glass, the ports leading to sources of supply of fuel and preheated combustion air. The combustion air is preheated by contact with refractory bricks heated by hot waste gases which have previously been withdrawn through checkerwork structures of a regenerator opposite the ports being fired. The direction of firing is periodically reversed, that is, the two series of ports are alternately operated so that first one series of ports is fired with the opposite series of ports serving to exhaust the hot waste gases. Then at periodic intervals, perhaps on the order of 20 to 30 minutes, the operating condition of the two series of ports is reversed, that is, the ports previously being fired serve as the exhaust ports and the ports exhausting the hot waste gases serve as the firing ports. Conventionally, the incoming combustion air and the hot exhaust gases are passed through checkerwork structures and associated tunnels extending the length of and lying beneath the checkerwork structures of the regenerators.
It is common practice to construct checkerwork structures of standard dimension, rectangularly shaped refractory bricks laid up in various arrangements commonly known in the art by the terms "basket weave," "open basket weave," "open-flue" and various other configurations. In addition to the above-mentioned heat exchange structures formed of standard dimension, rectangularly shaped refractory bricks, various types of specially shaped refractory bricks have been suggested for exclusive use in heat exchange systems. Examples of such bricks are disclosed in U.S. Pat. Nos. 4,436,144; 4,519,442 and 4,590,039. Generally, these specially shaped bricks which have been designed in an effort to achieve higher thermal efficiency for specific types of heat exchangers in given applications, have the disadvantage of being somewhat mechanically unstable when laid up in the checkers. Thus, as the checkers are repeatedly subjected to temperature changes over a period of time, the structure may fail.